Results of the National Research Programme "Sustainable Water Management” (NRP 61) suggest that the irregular decrease might be related to various degrees of silting in watercourses.
A significant proportion of the water we use comes from aquifers that are fed by infiltration along watercourses. River water temperatures have been rising regularly for several decades. By analysing data from municipal pumping stations, the Eawag researchers Simon Figura, David Livingstone and Rolf Kipfer have observed that this trend also extends to groundwater, where the average temperature increase is 0.3 to 0.6°C every ten years.Sawtooth decrease
A new analysis by the researchers now confirms that there is a trend towards lower levels of dissolved oxygen. As opposed to water temperatures, this decrease is not continuous but follows a sawtooth pattern: it is regularly interrupted by sudden increases that cannot be solely due to temperature.
By analysing the variations in water flow rate and the pumping volumes, the researchers have developed a new hypothesis: high river discharge and high pumping volumes lead to better river bed infiltration. This, in turn, leads to a swift increase in the oxygen concentration. However, it seems that this only happens after extreme spates that sweep away the silt on river beds. The spates thus clean the natural filter formed by river beds, which facilitates greater renewed infiltration and reoxygenation of the groundwater.
This hypothesis on the effects of the removal of riverbed silting is supported by field observations. During the 1970s, a layer of zebra mussels approximately five centimetres thick formed on the bed of the Rhine near to one of the pumping stations studied by the researchers. Several years later, divers noticed that the layer was no longer there. For this period, measurements indicate a clear increase in dissolved oxygen concentrations in aquifers.
(Available to journalists in PDF format from the SNSF: firstname.lastname@example.org)Contact
New study offers roadmap for detecting changes in the ocean due to climate change
20.08.2019 | Princeton University
New insight into glaciers regulating global silicon cycling
14.08.2019 | University of Bristol
Experimental progress towards engineering quantized gauge fields coupled to ultracold matter promises a versatile platform to tackle problems ranging from condensed-matter to high-energy physics
The interaction between fields and matter is a recurring theme throughout physics. Classical cases such as the trajectories of one celestial body moving in the...
Soft robots have a distinct advantage over their rigid forebears: they can adapt to complex environments, handle fragile objects and interact safely with humans. Made from silicone, rubber or other stretchable polymers, they are ideal for use in rehabilitation exoskeletons and robotic clothing. Soft bio-inspired robots could one day be deployed to explore remote or dangerous environments.
Most soft robots are actuated by rigid, noisy pumps that push fluids into the machines' moving parts. Because they are connected to these bulky pumps by tubes,...
Researchers at TU Graz are working together with European partners on new possibilities of measuring vehicle emissions.
Today, air pollution is one of the biggest challenges facing European cities. As part of the Horizon 2020 research project CARES (City Air Remote Emission...
Over the next three years, researchers from the Vrije Universiteit Brussel, University of Cambridge, École Supérieure de Physique et de Chimie Industrielles de la ville de Paris (ESPCI-Paris) and Empa will be working together with the Dutch Polymer manufacturer SupraPolix on the next generation of robots: (soft) robots that ‘feel pain’ and heal themselves. The partners can count on 3 million Euro in support from the European Commission.
Soon robots will not only be found in factories and laboratories, but will be assisting us in our immediate environment. They will help us in the household, to...
Scientists at the University of Leeds have created a new form of gold which is just two atoms thick - the thinnest unsupported gold ever created.
The researchers measured the thickness of the gold to be 0.47 nanometres - that is one million times thinner than a human finger nail. The material is regarded...
16.08.2019 | Event News
14.08.2019 | Event News
12.08.2019 | Event News
20.08.2019 | Life Sciences
20.08.2019 | Physics and Astronomy
20.08.2019 | Power and Electrical Engineering